Soft spinifex pastures in the Kimberley

Page last updated: Thursday, 7 June 2018 - 2:11pm

There are many different pasture types in the pastoral rangelands in the Kimberley region of Western Australia. The Department of Primary Industries and Regional Development (DPIRD) provides this pasture information to be used as a reference for assessing pasture condition, and as a guide for pastoral station staff and others interested in the productivity and maintenance of the pastoral rangelands.

Assessments can be used to monitor the success of management and to set goals for improving rangeland condition.

Soft spinifex pastures

Pastoral value

Soft spinifex pastures are of moderate grazing value under low stocking rates when in good condition. Soft spinifex pastures are the most useful of the spinifex pastures, and are also regarded as a useful drought reserve. Heavy grazing, or grazing too soon after fire, can remove the soft spinifex plants and cause condition decline.

Turpentine bush and other acacias may increase after fire, making it difficult for livestock to access the grass. Late-season burning on a 4- to 6-yearly rotation is considered to be good practice because it allows new seedlings to establish. The country should be spelled after burning until the grass seed has dropped.

Occurrence

Soft spinifex pastures are hummock grasslands with scattered trees and acacia shrubs. They occur on level to gently undulating plains, and occasionally hills, throughout the Kimberley. Soils are usually well-drained sands and loams, and are sometimes rocky.

Pasture condition

Good: The dominant grass is soft spinifex when this pasture type is in good condition. Other perennial grasses, including ribbon grass, silky browntop, curly spinifex and woollybutt grass, may occur in low numbers among the spinifex.

Annual grasses, such as limestone grass, may also be present. Plants are vigorous, productive and evenly spaced. The size and density of plants in the stand depends on the length of time since fire, seasonal conditions, grazing pressure and time of year.

Figure 1 Soft spinifex pasture in good condition in the Kimberley (photograph taken May 2008). A There is a high density of the desirable soft spinifex, and the plants appear healthy. B Young, soft spinifex plants are present; there is a good coverage of soft spinifex, given that this photo was taken about 2 years after the site was burnt.

Fair: As pasture condition declines from good to fair, less-desirable species, such as threeawns and wire grass, become more prominent, though soft spinifex is still dominant. Soft spinifex plants may be less vigorous and other desirable species are hard to find. Turpentine bush and other acacias may increase, making it difficult for livestock to access the grass.

Figure 2 Soft spinifex pasture in fair condition in the Kimberley (photograph taken May 2008). A The density of desirable soft spinifex is reduced, though it is still the dominant grass. B Other desirable grasses, such as silky browntop, are infrequent. C Undesirable threeawn grasses can be seen in the stand. D Turpentine bush has increased, reducing stock access to the grass. The soil surface still has good groundcover.

Poor: Soft spinifex pasture that has declined to poor condition will most likely be dominated by the undesirable species, threeawns, and wire grass, an intermediate species. There may be thick turpentine bush, making it difficult for livestock to access the grass, and bare areas may have increased. Where soft spinifex pasture in poor condition is adjacent to hard spinifex pastures, bare areas may be colonised by hard spinifex.

Figure 3 Soft spinifex pasture in poor condition in the Kimberley (photograph taken May 2008). A The desirable soft spinifex plants are sparse and lack vigour. B Hard spinifex, an undesirable species, has invaded the pasture; the undesirable annual threeawn is also present. C There are large bare areas. D There is a very thick stand of Halls Creek wattle and turpentine bush, which reduces livestock access to the grass and suppresses grass growth.